Certain tumors shed neoplastic cells into the blood before the primary tumor growth can be detected in the body. It has been shown recently that epithelial cells from the tumor can be detected in the blood at concentrations as low as 1 cell per ml of blood, and that the presence of rare cancer cells in blood has an important diagnostic value. The current screening methods are limited by relatively low speed of Fluorescent Activated Cell Scanning. (FACS),and complexity of preenrichment methods. The overall objective of this proposal is to develop a high-throughput, immunomagnetically based cell separating system to recover as many rare cancer cells in human blood as possible, for further molecular analysis (such as PCR, biological assays and other). The specific aims are as follows. First: the primary separation will be conduced using a novel continuos, flow-through immunomagnetic unit developed in our laboratories. Continuos units are intrinsically more efficient with respect to high throughput. We propose to develop experimental and theoretical basis for the next generation system which will sort cells at a rate of 10/7 cells/s, and allow a non- destructive screening of an entire volume of blood product used for cancer cell therapy ( typically 0.5 to 1.0 liters) in a short period of time (<1hour). Second: the continuos cell separation process can be staged, unlike the currently used batch systems. We propose to develop experimental and theoretical basis for the continuos staged separation process which will further increase the purity and decrease the volume of the cell product, and thus increase the rate of success of analysis downstream of the cell separation step. Third: the current cell labeling procedure may require modifications and optimization for the best performance in targeting and isolating rare cancer cells. We propose to screen available monoclonal antibodies and colloidal magnetic labels for the highest sensitivity and specificity in targeting rare cancer cells using unique Cell Tracking Velocimetry instrument developed in our laboratories. In summary, this proposal focuses on the "front-end" of cancer screening namely a high-throughoutput device to rapidly isolate and concentrate rare cancer cells form large numbers of cells. This proposal is responsive to PAR-98-067, Innovative Technologies for the Molecular analysis of Cancer, and we believe it addresses the second objective of the PAR, namely "novel technologies that will allow high- throughput analysis of genetic alterations, expression of genome products, and monitoring of signal transduction pathways to cancer."